Dual time point FDG-PET imaging is a successful technique for differentiating malignant from benign pleural disease

1757 Objectives: Dual time point imaging with FDG-PET has proven to be of value in assessing a variety of malignant disease by improving both the sensitivity and the specificity of the technique. The aim of this study was to assess whether FDG uptake and its change over time can be helpful in differentiating benign from malignant pleural disease. Methods: Twenty-eight consecutive patients (mean age= 61.4 years) with 38 PET studies were analyzed. They were referred for the evaluation of suspected malignant mesothelioma or recurrence of mesothelioma by FDG-PET imaging. All patients underwent two sequential PET scans (dual time point imaging) during each scan session. The mean time interval between the administration of 18FDG (5.2 Mbq / kg of body weight) and first scan was 60 minutes. The second time point image was acquired approximately 30 minutes following the initiation first set. The maximum standardized uptake value (SUV) of FDG was measured from the region of interest (ROI), which was placed at the site of the most active lesion on the PET scans from both time points (SUVmax1 and SUVmax2). The SUV measurements and PET results were correlated with follow-up histopathological biopsy results. Results: Among 28 patients, 23 were diagnosed with malignant mesothelioma according to histopathology and cytopathology results and they had a total of 33 dual time point PET studies with the follow up scans which resulted in detecting of 143 malignant lesions. The remaining 5 proved to have benign pleural disease. The average SUVmax1, the average SUVmax2 and the average percent maximum SUV changes over time of the 143 lesions in the malignant mesothelioma group were 5.3±2.51, 5.9±2.4 and 12.0±13.2% respectively. The corresponding values for the benign pleural disease group were 1.48 ±0.17, 1.32±0.20 and -14±22%. The average SUVmax1 and the average percent SUVmax changes in malignant mesothelioma was significantly higher than those in benign pleural disease group (p=0.002). Conclusions: Dual time point imaging demonstrates increasing levels of in 18FDG uptake over time in malignant mesotheliomas. Conversely, the uptake of 18FDG in benign pleural disease decreases with time. Therefore, it can differentiate benign from malignant pleural disease and is also helpful for guiding the biopsy site for a successful diagnosis. Dual time point imaging is a simple and noninvasive method that will likely improve the sensitivity and specificity of FDG-PET in detecting malignant pleural disease.